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Platinum Pt Notes


Platinum (Pt) General Information

Platinum is one of nine precious metals on the periodic table. It has a melting point of 1,772°C, a density of 21.4 g/cc, and vapor pressure of 10-4 Torr at 1,747°C. It is a radiant, silvery-white metal that bears a striking resemblance to palladium. It is dense, malleable, ductile, and corrosion resistant in air. Its most prominent commercial application is as a catalytic converter in vehicles. Platinum is evaporated under vacuum for the manufacture of semiconductors, fuel cells, and batteries. It is also utilized as a layer for optical coatings. Platinum is commonly found in jewelry and laboratory instruments.

Platinum Pt Specifications

Material TypePlatinum
SymbolPt
Atomic Weight195.084
Atomic Number78
Color/AppearanceMetallic Gray
Thermal Conductivity72 W/m.K
Melting Point (°C)1,772
Coefficient of Thermal Expansion8.8 x 10-6/K
Theoretical Density (g/cc)21.45
SputterDC
Max Power Density
(Watts/Square Inch)
100*
Type of BondIndium, Elastomer
Z Ratio0.245
E-BeamExcellent
Thermal Evaporation Techniques Crucible:  C
E-Beam Crucible Liner MaterialFABMATE®, Graphite
Temp. (°C) for Given Vap. Press. (Torr) 10-8:  1,292
10-6:  1,492
10-4:  1,747
CommentsAlloys with metals. Films soft, poor adhesion. Temperatures required to achieve deposition may not be practical for thermal evaporation.

* This is a recommendation based on our experience running these materials in KJLC guns. The ratings are based on unbonded targets and are material specific. Bonded targets should be run at lower powers to prevent bonding failures. Bonded targets should be run at 20 Watts/Square Inch or lower, depending on the material.

Z-Factors

Empirical Determination of Z-Factor

Unfortunately, Z Factor and Shear Modulus are not readily available for many materials. In this case, the Z-Factor can also be determined empirically using the following method:

  • Deposit material until Crystal Life is near 50%, or near the end of life, whichever is sooner.
  • Place a new substrate adjacent to the used quartz sensor.
  • Set QCM Density to the calibrated value; Tooling to 100%
  • Zero thickness
  • Deposit approximately 1000 to 5000 A of material on the substrate.
  • Use a profilometer or interferometer to measure the actual substrate film thickness.
  • Adjust the Z Factor of the instrument until the correct thickness reading is shown.

Another alternative is to change crystals frequently and ignore the error. The graph below shows the % Error in Rate/Thickness from using the wrong Z Factor. For a crystal with 90% life, the error is negligible for even large errors in the programmed versus actual Z Factor.